High-voltage pulse generator and circuits therefor



April 25, 1950 J. FUTTERMAN l 2,505,667

' HIGH-VOLTAGE PULSE GENERATOR AND CIRCUITS THEREFOR Filed Jan. 25, 19472 Sheets-Sheet l E g 234 fa. 26 u l q 7mm- LJN 22(4 23C ,B TIME- /276 QE ff E WM5-- l/ E 2f fz l o P l I@ ,(5 f-'a Y 2% wax/ff f5@ ATTORNEYApril 25, 1950 J. FUTTERMAN 2,505,667

-voLTAGE PQJLSE GENERATOR AND CIRCUITS THEREFOR HIGH 2 Sheets-Sheet 2Filed Jan. 25, 1947 fil/7577 L /QMP INVENTOR jl/L /us Fu TTERMH/VPatented Apr. 25, 1950 iA FFICE HIGH-VOLTAGE PULSE GENERATOR ANDCIRCUITS THEREFR Julius Futterman, New York, N. Y., assigner of one-halfto Joseph C. Ehrlich, New York, N. Y.

Application Januaryv 25, 1947, Serial No. 724,334

2 Claims. l

The present invention relates tothe art including electronic circuitsfor producing and utilizing high-voltage pulses, and more particularlyto such circuits operated from battery or other low-Voltage sources.

According to one feature of the invention, an extremely simple, light,and compact pulse generator is provided, adapted to be operated fromreadily portable batteries. to produce high-amplitude voltage pulses.

According to another feature of the present invention, a highlyefficient and readily portable high direct-voltage source is provided,excited only by low-voltage low-drain batteries, and useful, forexample, as a megohmmeter.

As a further feature of the present invention, a simple, inexpensive andconveniently portable repeater flash lamp is provided, useful forphotographic or other purposes, and providing readily controllable highintensity light flashes, repeatable at will very many times.

As still a further feature of the present invention, a simple and novelstarter and exciter for continuous high intensity arc lamps is providedwhich is very inexpensive to construct and operate, and which may beexcited either from alternating currentk or direct currentsources.

Accordingly, it is a majorobject oil the present invention' to provide anovel and vsimple highvoltagel pulse generator excited from relativelylow-voltage sources and of wide utility,l especially where portablehigh-voltage sources are required.

Itis a further object of thepresent invention toprovide an improvedV andnovel apparatus for converting low direct voltage to high directvoltage, without sacrificing portability and with high efficiency.

It is still another object of the present invention to provide improvedand novel exciter apparatus for flash or arc lamps utilizing. my novelpulse generator circuit.

Other objects andadvantages of` my inventionA will become apparent. fromthe followingV detailed description and the appended drawings, in whichFig. 1 is a schematic circuit diagram oi my novel pulsegenerator.

Fig. 2 is a series of current and voltage waveform curves useful inexplaining the operation oi my invention..

Fig. 3 isa schematiccircuit diagramk of my novel direct-voltage step-upconverter, incorporating a circuit similar to that ofA Fig. 1.

Figs. 4 and 5 are circuit diagrams of minor modiiications. ofthe circuitYof Fig. 3.

Fig. 6 is a circuit diagram of another embodiment of pulse generator,similar to Fig. 1.

Fig. is a schematic circuit diagram of my ini- ;oroved megohmmeterutilizing the principles of the preceding figures.

Fig. 8 is a schematic circuit diagram of my improved Iiash lamp exciter.

Fig. 9 is a schematic circuit diagram of my improved arc lamp exciterand starter.

Figure 1 shows a schematic Wiring diagram of one form of the pulsegenerator of the present invention. This generator comprises athermionic tube I9 which, for portability, is shown as being of thedirectly heated type having a filament or iilamentary cathode I I-energized from an A-battery I2. Tube Iii is shown as a triode having acontrol grid It and an anode or plats` I9, but it will be understoodthat the principles of the invention may be practiced with many otherforms of amplier tube, including tetrodes, pentodes, etc. A suitableiormof tube has been found to be the type 1LE3 which is a directly heatedtriode having a 1.4 volt, 50 milliampere filament, and operatingsatisfactorily with 67.5 or Volt Bf-batteries.

A high low loss, iron-cored coil I3 has one end I 4 connected to controlgrid I6, while the other end I5 of coil I3 is connected in series withswitch Il and B-battery I8 directly to plate I3. .An intermediate tap 2lof coil I3 is connected to the positive leg of filament II.

This extremely simple circuit has produced voltage pulses of extremelyhigh amplitude of the.

order of 2G00 to 4000 volts, from an ordinary B-battery of 67.5 or 90volts. The following explanation, referring to Figs. 1 and 2, isbelieved to represent the correct explanation of the theory of operationof my improved pulse-generating circuit. The curves of Fig. 2 representthe plate current I and the coil I3 primary and. secondary voltages E11and E2 as functions of time.

In these curves, E11 is taken as positive when lament II is positivewith respect to coil terminal I5, and E2 is positive when grid I6 ispositive relative to filament II.

Assuming that filament II is being heated by battery I2, and that switchIi is open, then obviously no plate current will flow, as indicated byportion 22a, 22h, 22e of the curves of Fig. 2. Switch Il is now closed,thereby permitting plate current I to flow under the inuence of theelectromotive force of battery I8. However, since battery I8 isconnected across the series inductance-resistance circuit provided bythe inductance oi the primary section P of coil I3 and the internalresistance of tube Il, in accordance with accepted circuit theory, thecurrent should rise in an exponential manner, if the resistance remainedconstant. However, due to changing grid voltage, the resistance of tubeI is not constant, and hence the plate current rises in a substantiallylinear manner, as shown by curve 23d of Fig. 2.

The primary voltage E1 is given both by the time rate of change ofcurrent I and by the difference between the battery voltage and the IRdrop in the tube resistance. This primary voltage initially risessteeply to a value shown at A in Fig. 2, and then slowly increases witha very small slope as shown at 23h. The substantially linear currentincrease 23a is thus accompanied by an almost constant primary inducedvoltage 23D.

The secondary voltage E2 is of course proportional to the inducedprimary voltage Ei, and thus has a similar wave form as at 23o. Sincevoltage E2 provides the sole bias for grid i6, grid I6 remainspositively biased and permits continued plate current rise for a time.However, the plate current cannot increase indefinitely; due to thecombined effects of grid current and plate current, a condition ofcurrent saturation is reached, where even further increase of positivegrid bias cannot further increase the plate current. As the platecurrent stops increasing, both the primary and secondary inducedvoltages drop to zero. This makes the grid more negative which reducesthe plate current. The decrease of plate current reverses the polarityof the secondary voltage E2 and thus cuts off the plate currentcompletely.

Once this action is started, upon E2 attaining the critical value (shownby point B) at which the increase in plate current is slowed down, theaction is cumulative and regenerative, to produce an extremely quickcurrent cut-off, equivalent to rapidly opening a switch. In view of thisrapid decrease of current, shown at 26a in Fig. 2, an extremely largenegative voltage pulse is developed across coil i3, as shown at 21h,21o. This voltage pulse has been found to be many times larger inamplitude than the voltage of battery i8. For example, with a batteryvoltage of 67 to 90 volts, pulses having amplitudes from 1000 to 4000volts have been obtained.

These pulses 2117 are of very short duration, and the voltages Ei and E2return to zero quick ly, since tube li is completely cut 01T. However,as the voltage E2 returns to Zero, tube iii begins to conduct, since itis conductive for zero bias. Hence the cycle just described starts allover again, and repeats itself periodically to produce periodic highintensity voltage pulses.

The frequency of these pulses is controlled by the inductance of thetransformer or coil i3. the plate resistance of tube I0, and the voltageof B battery itl. An increase in battery voltage decreases thefrequency. A decrease in tube resistance. as by substituting other tubetypes or by placing tubes in parallel, also reduces frequency. In normaloperation, frequencies from about 100 to 1500 pulses per second areencountered. In a representative circuit where the primary coil had aninductance of 5.36 henries and a Q of 25, the secondary coil had aninductance of 0.07 henry and a Q of 7.5, and with a turn ratio of about10.25 to l, the frequency was from 1000 to 1500 at a battery voltage of90 volts. The pulse voltage was around 1500 volts under theseconditions.

The intensity of the pulses 27h depends upon the interrelation betweenbattery voltage. tube amplification factor, and the ratio of primary tosecondary turns of coil i3. Too high a turn ratio has been found toprevent pulse generation completely. As the turn ratio is decreased, thepulse amplitude decreases, and the oscillations approach the sinusoidaltype produced by a regenerative oscillator. For best results, the turnratio is selected just below the cut-off value, so that theabove-described relaxation oscillations with high intensity pulses areproduced. For the 1LE3 tube at 90 volts, the primary to secondary vturnratio should be about 10 to 1.

Another critical factor has been found to be the resistance in thegrid-lament circuit. For best efficiency this resistance should be aslow as possible so that coil It, at least between terminals I4 and 2i,is of low resistance, and these terminals are directly coupled to gridand filament. Even a relatively small resistance has been found todecrease the pulse amplitude and conversion efficiency, while aresistance in the neighborhood of only 3000 ohms may stop pulseproduction entirely.

Gutput terminals for feeding the produced f pulses to external apparatusmay be connected in several different ways, so long as the primarywinding is coupled between them. Thus the following combinations arepossible: (l) between point I5 and filament; (2) between point I5 andgrid; (3) between filament and anode; (4) between grid and anode. Ofthese, (2) and (l) produce highest pulse intensity, which is onlyslightly higher than (1) or (3). (3) and (4) in* clude the batteryvoltage, and are useful where this is desirable.

The high voltage pulses produced by my novel circuit may be appliedwherever such pulses are found useful. In particular, they may berectified to produce a high direct voltage. In this way my invention isuseful as a direct current converter, and is especially useful as a Verylight, compact and portable source of high voltages of from 1000 to 4000volts, since the only power source required is supplied by a smallA-battery (1.5 volts) and a small B-battery (67.5-135 volts).

Fig. 3 shows such a portable high voltage source, using the pulsegenerator of Fig. 1. Connected in series between filament I I and anodeI9 are a rectifier tube 3l and a load resistor 32 bypassed by acondenser 33. Rectifier tube 3| is preferably of the same type as tubeI0, with low filament drain. The grid of rectifier 3l is tied to itsfilament to avoid breakdown between the closely spaced grid andfilament, due to the high voltage pulses. However, a diode rectifier mayalso be used here. The time constant of resistor 32 and condenser 33 ismade high enough so that, after only a short charge-up time, condenser33 is charged to substantially the peak amplitude of the voltage pulses.

A converter of this type has a very high conversion eiiiciency from lowvoltage to high voltage. Under the conditions described with respect toFig. 1, the circuit of Fig. 3 has produced conver- Sion eciences greaterthan 50%; that is, over 50% of the 90-volt power from battery i8 wasconverted to high-voltage power derivable at output terminals 35.

It will be understood that, where desirable, the resistance 32 may beprovided by a load coupled to terminals 35. It will also be understoodthat my invention is not limited to the particular type of rectiershown, since other types may also be used with equal or greatereffectiveness. In particular, so-called dry rectiers, such as of theacetico? selenium'orcopper-oxidetype, may also be used, as shownin Fig.4, Where dry rectifier Sla is used. In this ca'seoutput connection (l)is used, the rectifier 3Ifa and its load" resistor 32 being coupledbetweenv filament Il and the end l5 of coil I3. Fig. 5 shows a similarcircuit, using connection (2) described above, between grid and coil endI5. Of course, the other connections (3) and (4) can also be used Y It'is. to be noted that a single duplex tube, inclfudin'g both ampli'erand. diode sections, may be used' instead' of separate amplifier l0 andrectier 3| or 3io, with proper tube design to avoid breakdown.. betweencathode and diode anode due to` thelhigh pulse amplitudes.V

In the 'ab-ove embodiments of my invention, a single. tapped coil I3 hasbeen illustrated, used in a. circuit similarA to an auto-transformer.However, it'- will be apparent that a regular twowinding transformer canbe used equally well, as shown in Fig. 6, which shows the pulsegenerator circuit of'Fig. 1` with a transformer l3a having a primarywinding P and a secondary winding S substitutedfor the correspondingwindings of coil I3. Suchan arrangement avoids the necessity of couplingthe filament. directly to both primary and` secondary, as is exemplifiedin Fig, 6. It will be understoody that the secondary winding terminalsare connectedto theV grid and lament in the proper order to produce theaction described above with respect to Fig. 1-.

Output. is derived in Fig. 6 as in Fig. 1, from any of several pairs of.output terminals. One pair is shown in Fig. 6, coupled across primary P.These terminals could also be coupled between anode and lament orbetweenanode'and grid.

The pulsegenerating circuits of Figs. 1 and 6 are of course-capable ofother uses. In particular, by supplying a synchronizing or control pulsewave to the grid or plate, the frequency of the pulses produced byVthese circuits can be lockedin or synchronized with the control wave.Since the plate current is nearly a linear saw-tooth wave, this producesa synchronized saw-tooth wave useful for many purposes, such as intelevision.

Fig. 7 shows. the application. of my novel pulse generator `and highvoltage D.C. source in a portable megohmmeter. The pulse generator inthis ligure.- is thefsarne asin Fig. 6, with output taken from betweenanode and filament and applied to rectifier 35i inl series with a loadresistance comprising a plurality of series-connected voltagestabilizing lamps 35 in series with a small zeroadjusting potentiometer3l, both by-passed by lcondenser 33. Lamps 36 may be l/ze watt neonlamps, whichhave a stabilizing voltage of about 65-70 volts. Enoughlamps are connected in series to provide a desired output voltage, suchas 500 volts, suitable for megohmmeter use. The tap 38 of potentiometer31 is connected in series with a CalibratingY resistor 39 andmicroammeter 4l to one test lead 42, the other lead 42 being connectedtothe anode ofrectier 3|.

Inuse, test leads 42 are snorted together and tap 38 is varied untilmeter 4| reads full scale (corresponding to zero resistance across testleads 412). Then, with proper calibration of meter 4|, it will indicatedirectly the resistance of any circuit element connected to leads 42. Inview of the high voltage produced, very high resistances can bemeasured,in the megohm range, while retainingall the advantages of portabilityand compactness" characteristic of low-resistance ohmmeters.

i an ignition voltage of about 4000' volts;

Fig. 8 shows'this samecircult applied to control a'photographic flashlamp. In the photographic eld there is great needfor a simple andportable flash lamp capable` of' producing' readily con-- trollable,repeatable, short, intense flashes of light by-which photographs may betaken, without the necessity of replacing a liash bulb after eachpicture. Flash lamps suitable for this purpose are now commerciallyavailable (one form being known as the Sylvania type R4330 lamp), butthe portablek power supplies for theselamps are presently verycumbersome and weighty affairs, hardlypracticable for convenientportable use. However, by the use of the present invention, a verysimple flash unit is provided, which is very compact and Weighs only afew' pounds, including batteries.

The type H4330 lamp requires a. main discharge voltage yofrapproximately 2000 volts plus B'oth these voltages can bereadily'provided in a simple and novel manner by the use of the circuitof`Fig; 8, incorporating my novel pulse generator and high voltagesource. In Fig; 8, the same-pulse generator and rectifier circuit areshownk as in Fig. 7. However, the voltage stabilizing lamps 36 are newselected to provide about 2000 volts output, and a 2500 volt condenserw33/ of suitable capacitance, suchV as l0' microfarads or higher, isconnectedthereacrossz The hash lam-p 45: includes ka pair' of maindischarge electrodes 47, 48 connected across condenser and an ignitingMelectrode 4S connected to grid i t of tube F0.

A switch 5l is' connectedv in series' withA-battery i2l and serves as amaster switch, sincek no current can flow in any part of the circuitwhen switchi is open.

A secondv switch 53' is connected between the anode oi rectiiier 3l 'andcondenser 33, and serves as a hashV control switch. It will beunderstood that in actual use switch 53 is synchronized with the camerashutter release, in well-known manner.

in operation, flash-control switch 53 is normally closed. Hence, whenmain switch is rst closed, the pulse generator operates as describedabove to produce highV voltage pulsesy of the order of 400) volts inamplitude. These pulses are rectitled by rectifier 3i and charge-upcondenser 33. However, due to the shunting effect of stabilizing lamps3e, the Voltage across condenser 33 reaches only about 2000 volts in afew seconds and then remains at that value. The switch 5l is normallyclosed about 15 seconds before the i'lash is desired, to permitcondenser 355 to reach full charge. If desired, switch 53 may be anormally closed, momentary-open, type of switch.

It will be noted that condenser 33 is connected rdirectly across theVmain electrodes of iash tube 46, but is of insufiicient voltage toinitiate the discharge therein to produce the flash oi light. Forinitiating the flash, switch 53 is opened. By so doing, the full pulseamplitude of 4000 volts is impressed between igniting electrode 4e andmain electrode 4l, where previously only about 2060 volts had beenimpressed. This increase in potential of electrode 49 starts the maindischargebetween electrodes 41 and 48, which is raised to highintensity, producing a very intense light iiash, by the discharge ofcondenser 33 through the flash tube 4S.

After the iiash is produced, switch 53 is closed again, permittingcondenser 33 to recharge for the next ash. In this way readilycontrollable intense ashes are produced exactly when desired, by the useof a very light, compact and portable apparatus. These iiashes can berepeated many times without serious drain on the batteries, due to theremarkable eiciency of the voltage conversion, which is in theneighborhood of 50%.

While a major feature of the present invention is its extreme simplicityand lightness, making it extremely portable, the basic principles arealso adapted for use from power lines rather than with batteries. Such afurther use of my invention is shown in Fig. 9, which shows theinvention adapted for use to control an arc lamp from D.C. or A.C. powermains.

In Fig. 9 is shown schematically an arc lamp 6I which, for example, mayhave a 25 watt rating requiring 40 volts during continuous excitation,but which may require as much as 1000 to 2000 volts for starting. Thecircuit of Fig. 9 provides a very simple power supply for both startingand running such a lamp, from either A.C. or D.C. mains.

The essence of the circuit of Fig. 9 is a pulse generator similar tothat described above. However, in this circuit, for reasons given below,it is desirable to use a transformer I3a with very low resistanceprimary, preferably having low turn ratio. To obtain the advantages ofthe present invention with a lowered turn-ratio it is necessary to use atube having a high amplication factor, such as a pentode tube lila.

A bridge-type rectiiier 62 is coupled to the power mains by the plug B3through the main power switch 65 and has a filter condenser 64 connectedacross its output. The negative terminal of rectier 62 is connected tocathode 'Il of pentode ma. The positive terminal of rectiiier 62 isconnected through primary winding P to pentode plate 14. Secondarywinding S is connected between cathode 'Il and control grid 12.Suppressor grid 'l5 is connected directly to cathode 'H in conventionalmanner.

A single-pole double-throw switch 'I6 has its movable arm connected tothe positive rectier terminal and primary P, while the left switchterminal is connected to screen grid 'i3 and the right switch terminalis connected to plate 14. Arc lamp Si has one terminal connected to thenegative rectifier terminal while the other terminal is connectedthrough current-limiting resistor 'li to plate 14.

E55 is normally connected in the righthand position, where arc lamp Eiis connected directly across rectier 62, in its running condition. Inthis switch position, primary winding P is short-circuited, and nopotential is applied to screen grid l5, rendering the pulse generatorinoperative. However, for starting or restarting lamp Si, switch 'le ismomentarily moved to the left-hand position, thus unshorting primarywinding P and inserting it in series with arc lamp 6I. Simultaneouslyscreen grid 'i3 is energized from the positive rectiiier terminal, andtube 10d operates to produce high voltage pulses which ignite lamp 3l.Suilicient current then iiows from rectiiier t2 through primary P tomaintain lamp 6i illuminated. Upon returning switch 16 to the right-handposition, primary P is shorted 4out and lamp (il is restored to fullbrilliance. Preferably switch ii is of the type which is normally biasedto the right-hand position, and is depressed to put it into theleft-hand position; upon release it returns to the right positionautomatically. In *this way, the pulse generator is continually ready tostart or restart lamp 6|, merely by actuating switch 1S.

It will be apparent that the circuit of Fig. 9 is adapted for use eitherfrom A.C. or D.-C. mains, since rectier E2 offers only slight volt dropfor D.C. operation, which is immaterial to the operation ci my novelpulse generator.

In each of the above embodiments of my invention, it will be understoodthat several tubes may be connected in parallel if it is believeddesirable to increase the high-voltage power output 0r to increase thecharging rate of condenser 33 in Figs. 7 or 8.

Many other minor modifications of the abovedescribed circuits are, ofcourse, possible. For example, in Fig. 8, the starting electrode 49could be connected directly to filament ll instead of to control gridit, if desired. Also, as mentioned above, tube 3i could be replaced by adry rectier similar to 3 ia of Figs. 4 and 5. When using such a dryrectiiier 3m in the circuit of Fig. 8, other arrangements of rectifier,switch 53, and the combination of iiash lamp 46 and condenser 53 are, ofcourse, possible. For example, in one particular form, the same pulsegenerator circuit as shown in Fig. 8 or Fig. 6 can be used, and a seriesarrangement of condenser 33, a dry rectifier 3Ia and switch 53 isconnected, in that order, between the common terminal yoif batteries I2and I8 at one end and the plate i9 at the other end. It will beunderstood that stabilizing lamps 36 and the hash lamp llt are connectedin parallel with the condenser 33 as in Fig. 8. In addition, thestarting electrode 49 is connected directly to the plate i9. Thiscircuit provides the advantage that one terminal of the condenser and ofthe flash lamp is connected to the negative terminal of B- battery i3,which is normally grounded.

Other arrangements of the circuit are, of course, possible so long as,while switch 53 is closed, condenser 33 is charged to the limitingvoltage determined by stabilizing lamps 36, which voltage is appliedacross the principal electrodes 4l, t8, and, upon opening switch 53,this charging circuit is interrupted and the maximum pulse voltageproduced by the pulse generator circuit is applied between startingelectrode 49 and one of the principal electrodes 4l, 48. Other minormodifications will, of course, occur to persons skilled in the art.

Thus I have described an extremely simple, compact and light-weightcircuit adapted for portable use as a pulse generator as a low-voltageto high-voltage converter, as a megohmmeter, as a ilash lamp powersupply, as an arc lamp starter. However, it will be understood that manyother embodiments of the invention are possible all utilizing its basicprinciples, so that the foregoing description is to be taken asillustrative only, and not in a limiting sense.

I claim as my invention:

1. Flash lamp apparatus comprising a ash lamp having a pair of principalelectrodes and a starting electrode, and circuit means for igniting andflashing said lamp, said circuit means comprising a vacuum tube having agrid, a cathode and an anode, a source of direct current, a primary coilconnected in series with said source between said cathode and anode, asecondary coil connected directly between said grid and cathode, saidcoils being closely magnetically coupled and having a highprimary-to-secondary turn ratio, a series connection ci a rectifier anda load circuit therefor connected across said primary coil, saidprincipal flash lamp electrodes being connected across said loadcircuit, means connecting said starting electrode to said cathode, and aswitch in said series connection, whereby when said switch is closed ahigh direct voltage appears across said load circuit and upon openingsaid switch a large amplitude voltage pulse is impressed upon saidstarting electrode to start discharge of said direct voltage throughsaid lamp.

2. Flash lamp apparatus comprising a flash lamp having a pair ofprincipal electrodes and a starting electrode, in combination withcircuit means for igniting and flashing said lamp, said circuit meanscomprising a pulse generator circuit adapted to produce high-voltageperiodic pulses, the output circuit of said pulse generator including aseries connection of a rectifier, a switch and a condenser, saidcondenser being connected across said principal electrodes, meansconnected with said condenser for limiting its voltage to a valueincapable of initiating discharge between said pricipal electrodes,means responsive to 10 opening said switch for impressing the fullintensity of said pulses between said starting electrode and one of saidprincipal electrodes to initiate discharge in said flash lamp, wherebysaid condenser thereupon discharges through said ash lamp to produce ahigh-intensity light pulse thereby.

JULIUS FU'ITERMAN.

REFERENCES CITED The following references are of record in the le ofthis patenti UNITED STATES PATENTS Number Name Date 1,442,781 NicholsJan. 16, 1923 1,587,520 Hartley June 8, 1926 2,212,202 Faudell et al.Aug. 20, 1940 2,218,764 Moller et al Oct. 22, 1940 2,227,075 Geiger Dec.31, 1940

